1. Field of the Invention
The present invention relates to an apparatus and a method for Automatic Repeat reQuest (ARQ) in a wireless communication system. More particularly, the present invention relates to an apparatus and a method for generating an ARQ feedback message in a wireless communication system.
2. Description of the Related Art
Wireless communication systems are subject to data error according to the channel state of a radio resource carrying the data. To raise transmission reliability, the wireless communication systems generally control and recover the data error using an Automatic Repeat reQuest (ARQ) scheme.
Using the ARQ scheme, a receiving stage informs a transmitter stage of reception success or failure of an ARQ block received from the transmitting stage. For example, when the ARQ block received from the transmitting stage has no error, the receiving stage sends ACKnowledge (ACK) information to the transmitting stage. When the ARQ block received from the transmitting stage is erroneous, the receiving stage sends Negative ACK (NACK) information to the transmitting stage. A series of operations of the receiving stage informing the transmitting stage of success or failure in receiving the ARQ block is referred to as ARQ feedback. The receiving stage can carry out the ARQ feedback using a cumulative ACK scheme and a selective ACK scheme. Using the cumulative ACK scheme, the receiving stage transmits to the transmitting stage a sequence number of the last ARQ block of the ARQ blocks successfully received in succession. Using the selective ACK scheme, the receiving stage generates a bitmap indicating the reception success or failure of the ARQ block received from the transmitting stage and sends the bitmap to the transmitting stage.
When the ARQ block is given a variable length, the transmitting stage can divide the ARQ block into a plurality of ARQ sub-blocks and retransmit the ARQ sub-blocks to the receiving stage. In this case, the receiving stage needs to send ARQ feedback information of the ARQ block and ARQ feedback information of the ARQ sub-blocks to the transmitting stage. Accordingly, resources of the receiving stage for delivering the ARQ feedback information increase. When the transmitting stage generates the variable-length ARQ block, what is needed is a method for the receiving stage to efficiently transmit the ARQ feedback information of the ARQ block and the ARQ sub-block.